Imaging apparatus in which reduced resolution image data is generated, and when supplied over an image data bus, the resolution is increased and outputted

ABSTRACT

In an imaging apparatus, an image is to be displayed in real-time on a finder. In the finder mode, a CCD interface 21a thins out horizontal components of image data supplied from an image generating unit 10 to one-third and also effects gamma correction etc to send the resulting image data to a camera DSP 21c. The camera DSP 21c effects data conversion and resolution conversion on the image data resulting from the thinning to convert the data into Y, Cb and Cr image data which is routed to a memory controller 22. The memory controller 22 writes the image data in the image memory 32 and reads out the data from the memory controller 22 to route the read-out data over an image data bus 33 to an NTSC/PAL encoder 23. The NTSC/PAL encoder 23 converts the image data in resolution and further converts the image data into data of the NTSC or PAL system to route the resulting data to a finder.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an imaging apparatus having the function ofdisplaying an image of an object on a finder in real-time.

2. Description of the Related Art

A digital still camera retrieves image data obtained by a CCD imagesensor into a DRAM or a flash memory and subsequently transfers theimage data to a so-called personal computer or the like. A majorproportion of this type of the digital still camera has hitherto been ofthe type coping with the video graphics array (VGA) system.

Referring to FIG. 1, this digital still camera 200 includes a CCD imagesensor 201 for generating image signals, an input processing/imageprocessing circuit 202, a memory controller 203 for reading and writingimage data, an output processing circuit 204 for conversion to an outputimage of a pre-set system, a finder 205 for displaying the state of anobject at the time of image shooting, a recording unit 207 for recordingcompressed image data over a CPU bus 206 and a compression/expansioncircuit 208 for compressing/expanding image data. The digital stillcamera 200 also includes a memory 209, formed by, for example, a DRAM,and a CPU 210 for controlling the overall device.

Before starting the image shooting of an object, the user has to confirman object image displayed on the finder 205. This state is termed afinder mode. At this time, the CCD image sensor 201 sends image signalsobtained on photoelectric conversion of the imaging light from an objectto the input processing/image processing circuit 202. The inputprocessing/image processing circuit 202 performs the correlated dualsampling processing on the image signals to digitize the image signals.The input processing/image processing circuit 202 then performs pre-setsignal processing, such as gamma correction, knee processing or cameraprocessing and routes the processed image signals to the memorycontroller 203, which then is responsive to the control by the CPU 210to send the image data from the input processing/image processingcircuit 202 to the output processing circuit 204. The output processingcircuit 204 encodes image data in accordance with, for example, theNational Television System Committee (NTSC) system, and analogizes theencoded image data to route the resulting analog data to the finder 205.This allows the object as an object of image shooting to be indicated onthe finder 205.

On the other hand, if the user pushes a shutter button, not shown, toshift to the recording mode, the memory controller 203 causes the imagedata furnished from the input processing/image processing circuit 202 tobe written in the memory 209. The CPU 210 causes the image data to beread out from the memory 209 and compresses the image data from therecording unit 207 in the compression/expansion circuit 208 inaccordance with, for example, the Joint photographic Experts Group(JPEG) system to record the compressed image data in the recording unit207.

If the user performs pre-set processing to shift to the reproducingmode, the CPU 210 causes image data to be read out from the recordingunit 207 to cause the image data to be expanded in JPEG system in thecompression/expansion circuit 208 to route the resulting data via memorycontroller 203 and output processing circuit 204 to the finder 205. Thiscauses the as-shot image to be displayed on the finder 205.

In keeping up with recent outstanding technical progress in the CCDimage sensor, the resolution of image data is approximately surpassing1,000,000 pixels. On the other hand, it may be feared that the digitalstill camera of the above-described structure cannot sufficiently copewith the image data exceeding 1,000,000 pixels.

If, for example, the CCD image sensor 201 outputs image signals of highresolution in the finder mode, the input processing/image processingcircuit 202 has to perform resolution conversion of image data inreal-time in meeting with the resolution of the finder 205.Simultaneously, the memory controller 203 has to access the memory 209.The output processing circuit 204 also has to perform pre-setprocessing.

The result is stagnancy on the CPU bus 106, such that each circuitcannot execute pre-set processing in real-time and hence an image of anobject is displayed in a frame-decimated fashion on the finder 205. If,in this case, an object has made movements, there is produced deviationbetween the actual object and the movement of the object displayed onthe finder 105, thus producing an inconvenience in the imagingoperation.

On the other hand, if image data is not of high resolution, theresolution of the image data has to be converted into that of, forexample, the NTSC system or the PAL system, taking into account thesystem of the finder 205. In this case, it is similarly required todisplay an image on a finder in real-time.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an imagingapparatus in which, even of image data of an image are of highresolution, the image can be displayed in real-time on the finder.

In one aspect, the present invention provides an imaging apparatusincluding imaging means for generating image data corresponding to theimaging light from an object, first resolution converting means forlowering the resolution of the image data from the imaging means by wayof resolution conversion, second resolution conversion means for raisingthe resolution of the image data supplied from the first resolutionconversion means over an image data bus by way of resolution conversion,and outputting means for outputting the image data from the secondresolution conversion means on display means.

In another aspect, the present invention provides arecording/reproducing apparatus including imaging means for generatingimage data corresponding to the imaging light from an object,recording/reproducing means for recording the image data on a recordingmedium and for reproducing the image data recorded on the recordingmedium, first resolution conversion means for effecting resolutionconversion of lowering the resolution of the image data from the imagingmeans, second resolution conversion means for effecting resolutionconversion of raising the resolution of the image data supplied from thefirst resolution conversion means over an image data bus, storage meansfor storing the image data, third resolution conversion means forperforming resolution conversion of the image data supplied from thestorage means, and display means for displaying an image correspondingto the image data from the second or third resolution conversion means.

According to the imaging apparatus of the present invention, in which,by way of performing resolution conversion, the first resolutionconversion means lowers the resolution of the image data from theimaging means, and the second resolution conversion means raises theresolution of the image data supplied from the first resolutionconversion means over the image data bus to reduce the proportion ofoccupation of the image data on the image data bus to enable real-timedisplay of the object image on the display means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for illustrating the structure of aconventional digital still camera.

FIG. 2 is a block diagram showing a schematic structure of a digitalstill camera embodying the present invention.

FIG. 3 is a block diagram showing the schematic structure of the digitalstill camera shown in FIG. 2.

FIG. 4 is a block diagram for illustrating flow of image data in asignal processing unit of the digital still camera shown in FIG. 2.

FIG. 5 is a block diagram for illustrating the structure of a simplifiedresolution conversion circuit in an input processing circuit of thesignal processing unit.

FIG. 6 is a block diagram showing the structure of the resolutionconversion circuit of the signal processing unit.

FIG. 7 is a block diagram showing a specified structure of a horizontaldirection buffer, a horizontal direction conversion processing circuit,a vertical direction buffer and a vertical direction conversionprocessing circuit of the resolution conversion circuit.

FIG. 8 is a block diagram showing an alternative structure of theresolution conversion circuit.

FIG. 9 is a block diagram showing the structure of the verticaldirection buffer of the resolution conversion circuit.

FIG. 10 illustrates a technique for reading out image data from theimage memory by the memory controller.

FIG. 11 illustrates the coordinate position of pixels making up animage.

FIG. 12 illustrates another technique for reading out image data fromthe image memory by the memory controller.

FIG. 13 is a block diagram showing the structure of the horizontaldirection buffer of the resolution conversion c constituted by a linebuffer.

FIG. 14 illustrates the technique when the memory controller reads outimage data from the image memory.

FIG. 15 is a block diagram showing the structure of the simplifiedresolution conversion circuit in the NTSC/PAL encoder of the signalprocessing unit.

FIGS. 16A to 16F show a timing chart for illustrating the contents ofthe signal processing in the respective circuits in the finder mode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail.

The present invention is applied to digital still camera 1, configuredas shown for example in FIG. 2.

The digital still camera 1 includes an image generating unit 10 forgenerating image signals, an input signal processor 20 for processingimage data in a pre-set fashion, an image memory 32, comprised of anSDRAM, and a controller 40 for controlling the input signal processor20.

The image generating unit 10 includes a solid-state imaging device forgenerating image signals, such as a CCD image sensor 11, a sampleholding-analog/digital circuit (S/H-A/D circuit 12) for sample-holdingand digitizing the image signals to output image data, and a timinggenerator 13 for generating timing signals. This timing generator 13generates horizontal synchronization signals and verticalsynchronization signals for controlling respective circuits of the imagegenerating unit 10 based on synchronization signals supplied from thesignal processor input.

The CCD image sensor 11 generates image data corresponding to XGA(extended graphic array: 1024×768) pixel data made up of, for example,800,000 pixels. The CCD image sensor 11 is driven based on thesynchronization signals from the timing generator 13 to output imagesignals at a rate of 30 frames per second. Meanwhile, the CCD imagesensor 11 has the function of thinning out image signals and is able tothin out vertical components of the image signals to ½, ⅓, ¼, . . . tooutput the resulting thinned-out signals.

The S/H-A/D circuit 12 is also adapted to perform sample-holding and A/Dconversion at a pre-set sampling interval based on the synchronizationsignals from the timing generator 13 to send the resulting image data tothe signal processor 20.

The signal processor 20 includes a sole LSI (large scale integratedcircuit). The signal processor 20 includes an input signal processor 21for input processing and camera processing on image data from the imagegenerating unit 10, a memory controller 22 for controlling thereadout/write of image data for the image memory 32, an NTSC/PAL (phasealternation by line) encoder 23, a D/A converter 24 for analogizingimage data and outputting the resulting analog signals to outside, and async generator 26 for generating synchronization signals and supplyingthe resulting synchronization signals to the timing generator 13.

The signal processor 20 also includes a memory interface 27, as aninterface for the image memory 32, a resolution conversion circuit 28for converting the resolution of the image data, a JPEG (JointPhotographic Experts Group) encoder/decoder 29, forcompressing/expanding image data, a JPEG interface 30, as an interfaceof the JPEG encoder/decoder 29, and a host interface 31, as an interfacefor having data transmission/reception with the CPU of the controller40.

The input signal processor 21 processes the image data from the S/H-A/Dcircuit 12 with digital clamp, shading correction, aperture correction,gamma correction or color processing and routes the resulting processedsignals to the memory controller 22. The input signal processor 21 hasthe function of processing input data to convert the input data into Y,Cb and Cr. If the resolution of the image data is larger than that ofthe VGA (Video Graphics Array), the input signal processor 21 is able toperform the processing of lowering the resolution. The input signalprocessor 21 also performs the auto-focussing and auto-iris detection toroute the data to the controller 40 to effect automatic adjustment ofthe focussing mechanism and the iris mechanism. The input signalprocessor 21 also detects the signal level of the three prime colorsmaking up the image data to adjust automatic white balance.

The memory controller 22 also performs control to cause image datasupplied from the input signal processor 21 or other circuitry to bewritten in the image memory 32 via a memory interface 27 and to read outimage data of the image memory 32 via the memory interface 27. At thistime, the memory controller 22 detects whether or not there is anydefective pixel in the CCD image sensor 11 based on the image datastored in the image memory 32.

The memory controller 22 routes the image data read out from the imagememory 32 to, for example, the NTSC/PAL encoder 23. When fed with theimage data from the memory controller 22, the NTSC/PAL encoder 23encodes the image data in accordance with the NTSC system or the PALsystem to send the encoded data to the D/A converter 24. The D/Aconverter 24 analogizes the image data to output the resulting analogsignals via output terminal 25.

The memory controller 22 routes the image data, read out from the memorycontroller 22, to the resolution conversion circuit 28 to cause theimage data to be converted in resolution, while causing the image dataoutputted by the resolution conversion circuit 28 to be written in theimage memory 32.

The memory controller 22 routes the image data via the JPEG interface 30to the JPEG encoder/decoder 29 to effect compression of the still image,while causing the image data expanded by the JPEG encoder/decoder 29 tobe written in the image memory 32.

The image memory 32 not only stores the image data as described abovebut also stores OSD data (on-screen-display data) as the so-calledcharacter generator data. The OSD data is made up of bit map data. Thecontroller 22 controls the readout/write of the OSD data. The image dataand the OSD data are synthesized by the NTSC/PAL encoder 23.

The controller 40 includes a CPU (central processing unit) 41 forcontrolling the respective circuits of the signal processor 20, a DRAM(dynamic random access memory) 42, a ROM (read-only memory) 43, havingthe control program for the CPU 41 stored therein, a flash memoryinterface 44, as an interface for exchanging image data with a storagedevice 51, such as a flash memory, and an IrDA interface 45, as aninterface of the communication circuit 52 constituted such as by IrLED.

For example, the CPU 41 causes image data compressed by the JPEGencoder/decoder 29 to be written via a flash memory/interface 44 in astorage device 51, made up of a flash memory, while causing image datato be read out from the storage device 51 to route the image data readout from the JPEG encoder/decoder 29. The CPU 41 also causes the imagedata read out from the storage device 51 to be outputted via the IrDAinterface 45 and the communication circuit 52 as infrared light tooutside.

The schematic structure of the digital still camera 1 is shown in FIG.3.

The input signal processor 21 routes the image data from the CCD imagesensor 11 via an image data bus 33 to the image memory 32. The NTSC/PALencoder 23 encodes the image data from the image memory 32 in a pre-setfashion to send the resulting encoded data to the finder 36. This causesan image of an object to be displayed on the finder 36 which is adaptedto display the image in association with the image data up to the VGAformat.

The memory controller 22 performs data transfer between the image memory32 and the signal processing circuits connecting to the image data bus33. The resolution conversion circuit 28 performs resolution conversionof the image data from the image memory 32 to route the results to theimage memory 32. The JPEG encoder/decoder 29 compresses the image datafrom the image memory 32 in accordance with the JPEG system to route thecompressed image data via CPU bus 34 to the CPU 41, which then causesthe compressed image data to be written in the storage device 51. TheCPU 41 is also able to output the compressed image data via the CPU bus34 and the communication circuit 52 to outside.

Thus, is FIG. 3, the respective circuits of the signal processor 20 areinterconnected over the image data bus 33. The image data bus 33 is avirtual bus and indicates that there is placed a limit to the transferband for image data exchanged between the respective circuits.

In the signal processor 20, the respective circuits, such as NTSC/PALencoder 23 or the resolution conversion circuit 28, send to the memorycontroller 22 a request signal indicating that image data are demanded.These circuits also transmit a request signal to the memory controller22 when outputting the image data after the end of the processing of theimage data.

On reception of the request signals from the respective circuits, thememory controller 22 selects those circuits having the high prioritysequence, and transmits an acknowledge signal to the selected circuit.The acknowledge signal indicates that image data can be routed to acircuit receiving the signal or that image data outputted by a circuitwhich has received the acknowledge signal is ready to be received. Thememory controller 22 reads out image data from the image memory 32 toroute the read-out image data via image data bus 33 to the circuitcorresponding to the destination of the acknowledge signal. The memorycontroller 22 receives the image data outputted by the circuit which hassent the acknowledge signal to write the image data in the image memory32.

On reception of the request signals from plural circuits, the memorycontroller 22 is able to select preferentially the circuit which has toperform the processing in real-time. For example, if an image of anobject is to be displayed on the finder 36, the memory controller 22preferentially selects the input signal processor 21 and the NTSC/PALencoder 23. It is also possible for the memory controller 22 to decipherthe bus occupation ratio of the image data on the image data bus 33 todetermine the priority sequence of the respective circuits depending onthe occupation ratio.

If image data can be routed to the respective circuits within thetransfer band limitation of the image data bus 33, it is possible forthe memory controller 22 to perform control to send the acknowledgesignal to the respective circuits time-divisionally to permit therespective circuits to perform pre-set processing. This enables thememory controller 22 to have access in real-time to data in therespective circuits to cause the image data from the respective circuitsto be written in the image memory 32 or to cause the image data in theimage memory 32 to be read out and sent to the respective circuits.

If, when the memory controller 22 has access to external circuitry, notshown, over the image data bus 33, the external circuitry can send theabove-mentioned request signal or receive the transmitted acknowledgesignal, the memory controller 22 can have access simultaneously andtime-divisionally to the respective circuits within the signal processor20 within the transfer band limitation range of the image data bus 33.That is, if within the range of the band of the image data bus 33, thememory controller 22 can have simultaneous access to the circuits in thesignal processor 20 or to the external circuits within the signalprocessor 20 time-divisionally without regard to the number of thecircuits within the signal processor 20 or the external circuit.

As mentioned above, the memory controller 22 performs arbitration of theimage data bus 33, write/readout control of image data between the imagememory 32 and the respective circuits and data transfer to the CPU bus34.

The specified flow of image data in the signal processor 20 is explainedwith reference to FIG. 4.

The input signal processor 21 includes a CCD interface 21 a forperforming pre-set signal processing on the image data from the imagegenerating unit 10, a detection circuit 21 b for processing the CCDinterface 21 a, and a camera digital signal processor 21 c (camera DSP21 c) for doing conversion processing of the image data.

The CCD interface 21 a performs the processing, such as the digitalclamp, white balance adjustment or gamma correction, on the image datamade up of R, G and B from the S/H-A/D circuit 12 shown information FIG.2, or decimates the components in the horizontal direction of image datain case of necessity. After such processing, the CCD interface 21 aroutes image data to the camera DSP 21 c or to the memory controller 22via the image data bus 33.

From the image data of the CCD interface 21 a, the detection circuit 21b performs detection for auto-focussing, auto-iris or white balanceadjustment.

The camera DSP 21 c converts the image data of R, G and B from the CCDinterface 21 a into image data made up of luminance signal Y andchrominance signals Cb, Cr. The camera DSP 21 c also has a simplifiedresolution conversion circuit 21 which not only performs the aboveprocessing but also converts the resolution of the image data in asimplified fashion.

The simplified resolution conversion circuit 21 d operates forconverting the resolution of the image data to lower values if theresolution of the image data generated by the CCD image sensor 11 islarger than, for example, the VGA format.

Specifically, the simplified resolution conversion circuit 21 d includesa B−Y/R−Y separation circuit 61, for separating chrominance signals, ahorizontal direction linear interpolation circuit 62 for interpolationin the horizontal direction, a B−Y/R−Y synthesis circuit 63 forsynthesizing the chrominance signals, a 1H delay circuit 64 for delayingthe respective signals by a horizontal scanning period (1H period), anda vertical direction linear interpolation circuit 65.

The B−Y/R−Y separation circuit 61 separates the chrominance signals B−Yand R−Y, as chroma signals Cb, Cr, from the image data from the cameraDSP 21 c, to route the separated chroma signals to the horizontaldirection linear interpolation circuit 62. The horizontal directionlinear interpolation circuit 62 interpolates the luminance signals Y andthe chrominance signals B−Y, R−Y in the horizontal direction to lowerthe luminance in the horizontal direction to route the interpolatedluminance signals Y and the chrominance signals B−Y, R−Y to the B−Y/R−Ysynthesis circuit 63.

The B−Y/R−Y synthesis circuit 63 synthesizes the chrominance signalsB−Y, R−Y, to route the luminance signals Y from the horizontal directionlinear interpolation circuit 62 and the synthesized chrominance signalsB−Y, R−Y to the 1H delay circuit 64 and to the vertical direction linearinterpolation circuit 65. The 1H delay circuit 64 delays the luminancesignals Y and the chrominance signals by 1H to route the delayed signalsto the vertical direction linear interpolation circuit 65. The verticaldirection linear interpolation circuit 65 performs linear interpolationprocessing in the vertical direction, based on the luminance signals Yand the chrominance B−Y, R−Y from the B−Y/R−Y synthesis circuit 63 andthe 1H delay circuit 64, to output image data made up of luminancesignals Y′ and chrominance signals (B−Y)′, (R−Y)′ lowered in resolutionin both the horizontal and vertical directions.

The resolution conversion circuit 28 performs resolution conversionprocessing of converting [p×q] image data into [m×n] image data. Theresolution conversion circuit 28 performs processing for suppressing theresolution to a pre-set value if the image data produced in the CCDimage sensor 11 are of high resolution. It is however possible toprocess the image data of low resolution into data of high resolution.

Referring to FIG. 6, the resolution conversion circuit 28 includes aninput buffer 71 for storing image data, inputted from the image data bus33, a horizontal direction buffer 72, for buffering the image data fromthe an input buffer 71 in the horizontal direction, a horizontaldirection transform processing circuit 73 for converting the resolutionof the image data from the horizontal direction buffer 72 in thehorizontal direction, a vertical direction buffer 74 for buffering theimage data from the horizontal direction transform processing circuit 73in the vertical direction, a vertical direction transform processingcircuit 75 for converting the resolution of the image data in thevertical direction, and an output buffer 76 for buffering at the time ofoutputting.

When ready for converting the resolution of the image data, theresolution conversion circuit 28 outputs a read request signalrequesting the memory controller 22 to read out image data from theimage memory 32, while outputting a write request signal requesting thememory controller 22 to write the image data in the image memory 32after the conversion processing of the image data. The resolutionconversion circuit 28 also receives an acknowledge signal indicatingthat the memory controller 22 has responded to the request signal.

Referring to FIG. 7, the horizontal direction buffer 72 is made up of afirst delay circuit 81, a second delay circuit 82 and a third delaycircuit 83 each for producing the delay of one pixel. Thus, the firstdelay circuit 81 outputs image data delayed by one pixel, while thesecond and third delay circuits 81, 82 output image data delayed by twopixels and image data delayed by three pixels, respectively.

Referring to FIG. 7, the horizontal direction transform processingcircuit 73 includes first to fourth multipliers 84, 85, 86, 87, andfirst to third adders 88, 89, 90. A circuit for normalizing data isincidentally annexed at back of the adder 90.

The first multiplier 84 multiplies the image data supplied from the aninput buffer 71 with a pre-set coefficient to route the resulting datato the adder 88. The second multiplier 85 multiplies the image datasupplied from the first delay circuit 81 with a pre-set coefficient toroute the resulting data to the adder 88. The third multiplier 86multiplies the image data supplied from the second delay circuit 82 witha pre-set coefficient to route the resulting data to the adder 89. Thefourth multiplier 87 multiplies the image data supplied from the thirddelay circuit 83 with a pre-set coefficient to route the resulting datato the adder 90. The first adder 88 synthesizes the image data to sendthe resulting data to the second adder 89. The second adder 89synthesizes the image data to send the resulting data to the third adder90. The third adder 90 synthesizes the respective image data to send theresulting data as image data converted in resolution in the horizontaldirection to the vertical direction buffer 74.

Thus, the horizontal direction transform processing circuit 73 weightsplural image data each having one pixel delay in a pre-set fashion withpre-set weights and synthesizes the weighted image data to interpolateor decimate the pixels in the horizontal direction to convert theresolution in the horizontal direction.

The vertical direction buffer 74 is constituted by a serial connectionof first to third buffers 91, 92, 93, each adapted to produce a one-linedelay. Thus, the first bufer memory 91 outputs image data delayed by oneline, while the second and third buffer memories 92, 93 output the imagedata delayed by two and three lines, respectively.

Referring to FIG. 7, the vertical direction transform processing circuit75 includes fifth to eighth multipliers 94 to 97 and fourth to sixthadders 98 to 100. The vertical direction transform processing circuit 75occasionally includes a circuit for nonrmalizing data on the downstreamside of the adder 90.

The fifth multiplier 94 multiplies the image data supplied from thehorizontal direction conversion circuit 73 with a pre-set coefficient toroute the resulting data to the fourth adder 98. The sixth multiplier 95multiplies the image data supplied from the first line memory 91 with apre-set coefficient to route the resulting data to the fourth adder 98.The seventh multiplier 96 multiplies the image data supplied from thesecond line memory 92 with a pre-set coefficient to route the resultingdata to the fifth adder 99. The eighth multiplier 97 multiplies theimage data supplied from the third line memory 93 with a pre-setcoefficient to route the resulting data to the sixth adder 100. Thefourth adder 98 synthesizes the image data to send the resulting data tothe fifth adder 99. The fifth adder 99 synthesizes the image data tosend the resulting data to the sixth adder 100. The sixth adder 100synthesizes the respective image data to output the resulting data asimage data converted in resolution in the horizontal direction.

Thus, the vertical direction transform processing circuit 75 weightsplural image data each having one line delay in a pre-set fashion withpre-set weights and synthesizes the weighted image data to interpolateor decimate the pixels in the horizontal direction to convert theresolution in the vertical direction.

In FIG. 7, the resolution conversion circuit 28 first performsresolution conversion in the horizontal direction followed by resolutionconversion in the vertical direction. It is however possible for theresolution conversion circuit 28 to perform resolution conversion in thevertical direction followed by conversion in the horizontal direction.That is, the resolution conversion circuit 28 may be configured tosupply the image data from the input buffer 71 to the vertical directionbuffer 74 and to effect the processing in the vertical direction buffer74, vertical direction transform processing circuit 75, horizontaldirection buffer 72 and in the horizontal direction transform processingcircuit 73, in this order.

In the above-described embodiment, the first to third buffer memories 91to 93 in the vertical direction buffer 74 are configured to storeone-line (1H) image data. Alternatively, the first to third buffermemories 91 to 93 may be configured for storing image data lesser thanone line, as shown in FIG. 9. It is then necessary for the memorycontroller 22 to read out the image data stored in the image memory 32every N pixels, as shown in FIG. 10.

Specifically, the memory controller 22 reads out pixel datacorresponding to a viewing screen stored in the image memory 32 every Npixels on the line basis in the vertical direction. Referring to FIG.11, each viewing screen is made up of p×q pixels, with the coordinate ofthe upper left pixel being (1,1), that of the upper right pixel being(p,1), that of the lower left pixel being (1,q) and with the lower rightpixel being (p,q).

Referring to FIG. 12, the memory controller 22 causes the image data ofN pixels to be read out on the line basis in the horizontal direction inthe sequence of the rows 1, 2, . . . , q. This causes the memorycontroller 22 to read out image data corresponding to N pixels from theleft end, or N×q pixels, that is pixel data in an area defined by (1,1),(1,q), (N,q) and (N,1). This image data is referred to below as imagedata set (1).

The memory controller 22 then reads out image data in a range defined by(N−1,1) (N−1, q), (2N−2, q), (2N−2, 1), referred to below as the imagedata set (2). If the memory controller 22 reads out the image data set(1) and the image data set (2), it is tantamount to reading out theimage data of the (N−1)st column and the Nth column twice.

The reason is that, since the vertical direction transform processingcircuit 75 performs interpolation beginning from the surrounding pixel,the pixels stored in the beginning end and the trailing end of the firstto third buffer memories 91 to 93 are not the object of processing. Forexample, if the image data set (1) is read out, the pixel (N, 1) is notthe object of the interpolation processing in the vertical direction.However, this pixel (N, 1) is read out when the pixel data set (2) isread out, and becomes the object of interpolation processing.

In similar manner, the memory controller 22 reads out image data of Npixels in the horizontal direction every line so that image data of thelast two columns of the directly previous image data set will beincluded. This routes the image data set to the resolution conversioncircuit 28.

The vertical direction buffer 74 is fed with image data, in an amountcorresponding to the capacity of the first to third buffers 91 to 93, onthe line basis. Thus, image data offset one line is stored in each f thefirst to third buffer memories 91 to 93. The vertical directiontransform processing circuit 75 is able to perform the resolutionconversion processing in the vertical direction based on the image datafrom the first to third buffers 91 to 93 of the vertical directionbuffer 74.

With the memory controller 22, the memory controller 22 can cause theresolution conversion circuit 28 to execute the resolution conversion inthe vertical direction, by readout in meeting with the capacity of thebuffer memory, even if the capacity of the buffer memory required forresolution conversion in the vertical direction is not up to one line.

Although the read-out overlap between the image data sets is twocolumns, it is probable that the overlap exceeds two columns or there isno overlap. It is noted that the present invention is applicable toimage signal processing, such as camera signal processing, withoutlimitation to resolution conversion.

Although the foregoing description is directed to the embodiment inwhich the buffer memory is being used for interpolation for the verticaldirection, the present invention is also applicable to an embodiment inwhich the buffer memory is being used for interpolation for thehorizontal direction.

That is, the resolution conversion circuit 28 may perform resolutionconversion in the horizontal direction using a horizontal directionbuffer 72 a comprised of a buffer memory 72 a having a capacity of Npixels, as shown in FIG. 13. The memory controller 22 can read out imagedata of N pixels on the column basis in the sequence of the rows 1, 2, .. . , p in the vertical direction, as shown in FIG. 14. Meanwhile, it isnecessary for the memory controller 22 to read out the image data storedat the leading and trailing ends of the buffer memory twice, as in theabove-described vertical interpolation processing, so that these imagedata will be the object of the horizontal interpolation processing.

Thus, the memory controller 22 is able to read out image data from theimage memory 32 so that resolution conversion processing in thehorizontal and vertical directions will be effected for the first tothird buffer memories 91 to 93 each having a capacity of N pixels. Thisenables the circuit scale of the horizontal direction buffer 72 and thevertical direction buffer 74 to be reduced to lower the production cost.

The NTSC/PAL encoder 23, executing the encoding as described above, alsohas a simplified resolution conversion circuit 23 a for increasing theresolution of the image data, if need be, before proceeding to encoding.

The simplified resolution conversion circuit 23 a performs resolutionconversion for matching to the display standard of the finder 36 if theimage data on the image memory 32 is lower than the resolution requiredfor display.

Referring to FIG. 15, the simplified resolution conversion circuit 23 aincludes a line memory 101 for storing image data from the image databus 33, a vertical direction linear interpolation circuit (V-directionlinear interpolation circuit 102) for interpolating image data in thevertical direction, and a horizontal direction interpolation circuit103.

The line memory 101 stores image data from an input terminal in in anamount corresponding to one line to send the image data to theV-direction linear interpolation circuit 102 in the order it is stored.The V-direction linear interpolation circuit 102 weights the image datafrom the input terminal in and the image data from the V-directionlinear interpolation circuit 102 with a pre-set weighting to performlinear interpolation in the vertical direction. The horizontal directioninterpolation circuit 103 interpolates Y with an order-seven filter,while interpolating Cb and Cr with an order-three filter. This is simplythe interpolation for increasing the resolution by a factor of two. Thehorizontal direction interpolation circuit 103 outputs the image data atan output terminal out.

For example, if image data inputted from the input terminal in isdenoted a, image data read out from the line memory 101 is b, acoefficient for weighting is g, where 0≦g≦1, and image data outputted bythe V-direction linear interpolation circuit 102 is c, the V-directionlinear interpolation circuit 102 effectuates the following processing:

c=g*a+(1−g)*b.

The image data outputted by the output terminal out is encoded by theNTSC/PAL encoder 23, as mentioned previously.

In the signal processing system, the digital still camera 1 is made upof so-called two chips, namely s signal processor 20 and a CPU 41.Therefore, the respective signal processing circuits are each of thechip configuration, so that the substrate surface area and further thepower consumption can be made smaller than if the respective signalprocessing circuits are of separate chip configurations.

Also, since the signal processor 20 is not of the chip configurationinclusive of the CPU, signal processing can be adaptively effectuatedeven if the application in connection with the CPU 41 is changed. Thatis, if the signal processor 20 is of the chip configuration inclusive ofthe CPU, it is impossible to reconstruct the chip in case theapplication of the CPU is changed. However, the signal processor 20 canperform the pre-set signal processing using a CPU of an optimumstructure on the application basis.

The digital still camera 1 of the above-described structure has a findermode for confirming the status or the position of an object prior toimage shooting, a recording mode for shooting the image of the object asconfirmed, and a reproducing mode for confirming the shot state of theobject image, and effects the processing depending on the prevailingmode.

In the finder mode, the user has to observe the state of the objectindicated on the finder 36 before thrusting a shutter button, not shown,to shoot the object. In this finder mode, the memory controller 22 andother circuits are controlled in the following manner. For illustratingthe respective modes, reference is had mainly to FIG. 4 and occasionallyto FIG. 16.

In the finder mode, the CCD image sensor 11 generates image signals,thinned out to one-third from the vertical components, and furnishes thedigitized image data via the S/H-A/D circuit 12 to the CCD interface 21a.

The CCD interface 21 a performs signal processing in synchronism withclocks shown in FIG. 16A. Specifically, the CCD interface 21 a decimatesthe horizontal components of the image data supplied by the imagegenerating unit 10 to one-third and corrects the decimated image datafor gamma to send the gamma-corrected data to the camera DSP 21 c. TheCCD interface 21 a furnishes the image data converted to 340×256 fromthe ⅓ decimation process to the camera DSP 21 c.

The camera DSP 21 c performs data conversion processing on the decimatedimage data into YCrCb image data. The camera DSP 21 c converts theresolution of the image data in the simplified resolution conversioncircuit 21 d (340×256→320×240) for lowering the resolution of the imagedata to route the converted image data via image data bus 33 to thememory controller 22.

It is noted that the simplified resolution conversion circuit 21 dlowers the resolution in a simplified fashion to an extent necessary forsubsequent processing. In this manner, if image data generated by theCCD image sensor 11 is of high resolution, the transfer range taken upby the image data generated by the CCD image sensor 11 can be decreasedto evade the stagnancy on the image data bus 33 to maintain thereal-time characteristics of the finder mode.

The memory controller 22 writes the image data in the image memory 32,while reading out the image data from the image memory 32 as shown inFIG. 16D to send the read-out image data via the image data bus 33 tothe NTSC/PAL encoder 23. Simultaneously, the memory controller 22 readsout the OSD data stored in the image memory 32, as shown in FIG. 16E, tosend the OSD data stored in the image memory 32, as shown in FIG. 16E.FIG. 16F shows the state of transfer on the image data bus 33 whichenables the above-described real-time processing.

The NTSC/PAL encoder 23 performs resolution conversion of320×240→640×240 or 320×240→640×288 in the case of the NTSC system or thePAL system, respectively, to send the converted image data to theNTSC/PAL encoder 23. The NTSC/PAL encoder 23 also converts the imagedata into data of the NTSC system or the PAL system into OSD data whichis routed to the finder 36 shown in FIG. 3. This allows the image of theobject and the title information etc to be displayed in-real time on thefinder 36.

Meanwhile, the NTSC/PAL encoder 23 converts the resolution so that datawith low resolution will be increased in resolution, such that, if320×200 image data is furnished, it is converted into 640×240 image dataand into 640×288 image data for the NTSC system and for the PAL system,respectively.

In the digital still camera 1, the resolution of the image datagenerated by the CCD image sensor 11 is lowered in a simplified fashionin the finder mode to reduce the data volume, so that the image datawill be within the bandwidth limitation of the image data bus 33 and sothat the resolution will be increased at an output stage to the extentthat is necessary for display, at a timing shown in FIG. 16F.

Thus, with the digital still camera 1, the image data is held in thebandwidth limitation of the image data bus 33 to permit the image of theobject to be displayed on the finder 36, even if the image data is ofhigh resolution, without the necessity of performing the time-consumingdecimation processing.

If the circuitry for preferential processing, namely the CCD interface21 a, camera DSP 21 c or the NTSC/PAL encoder 23, is previously set inthe CPU 41, and signal processing is carried out time-divisionally inother circuits as in the above circuits, the processing of therespective circuits with high priority may be preferentially performeddepending on the data volume of the image data.

In the event of the large data volume of the image data in thesimplified resolution conversion circuit 21 d, data processing may beperformed at a high processing speed, in order to give priority toreal-time processing, even though the picture quality is degraded to acertain extent, under control by the CPU 41. In this manner, high-speedprocessing can be effected in the finder mode even in case of the largedata volume of the image data generated in the image generating unit 10.

In the case of the digital still camera 1, having an electronic zoomingfunction, the CPU 41 can control the respective circuits in thefollowing manner.

The memory controller 22 causes the image data, supplied via the CCDinterface 21 a and camera DSP 21 c, to be written in the image memory32, while causing the image data to be read out from the image memory 32and routed to the resolution conversion circuit 28. The resolutionconversion circuit 28 formulates image data enlarged from a portion ofthe input image, by an electronic zooming function, to output theresulting image data to the image memory 32. This image data is read outfrom the image memory 32 and outputted to the finder 36 via the NTSC/PALencoder 23. This generates electronically zoomed image data.

Since the finder mode gives utmost priority to the real-timecharacteristics, time-consuming processing is not executed by therespective circuits. However, the CPU 41 can be configured to cause thememory controller 22 and other circuits to perform various processingoperations if within the range allowed by the transfer area of the imagedata bus 33.

For example, the memory controller 22 may be configured to read outimage data from the image memory 32, in which is stored the image datafurnished from the CCD interface 21 a, and to furnish the read-out imagedata to the NTSC/PAL encoder 23 over the image data bus 33 and to theJPEG encoder/decoder 29. The finder 36 displays the image of the objectin rea-time, while the JPEG encoder/decoder 29 compresses the image datain accordance with the JPEG system.

The JPEG encoder/decoder 29 compresses/expands the still image, while itcannot process high-pixel image in real-time. It is thus possible forthe JPEG encoder/decoder 29 to decimate a pre-set number of frames ofthe image data supplied from the image data bus 33 (number of frames orfields) by way of compression or to slice a portion of the image tolower the resolution by way of compression. This enables shooting of aframe-decimated still image continuously or shooting of a low-resolutionimage continuously.

The user observes the state of the object displayed on the finder 36 inthe above-mentioned finder mode. If the object is decided to be shot,the user pushes a shutter button, not shown.

If the shutter button is pushed, the digital still camera 1 proceeds tothe recording mode. In the recording mode, the CPU 41 controls thememory controller 22 or the respective circuits in the following mannerto record the image of the as-shot object on a recording device 51.

The CCD image sensor 11 halts the decimation operation in synchronismwith the thrusting the shutter button to generate image signals of theXGA format to route the digitized image data via the S/H-A/D circuit 12to the CCD interface 21 a.

The CCD interface 21 a routes the image data furnished from the S/H-AIDcircuit 12 not to the camera DSP 21 c, but to the memory controller 22via the image data bus 33. The memory controller 22 first writes theimage data in the image memory 32 and subsequently reads out the imagedata to route the read-out image data via the image data bus 33 to thecamera DSP 21 c. The camera DSP 21 c converts the image data made up ofRGB into image data made up of Y, Cb and Cr.

The camera DSP 21 c is fed with image data once written in the imagememory 32. That is, the camera DSP 21 c effects data conversion on theimage data from the image memory 32 instead of on the image datadirectly supplied from the CCD interface 21 a. Thus, it is unnecessaryfor the camera DSP 21 c to perform high-speed data conversion, but it isonly sufficient if the camera DSP 21 c executes such processing when theimage data bus 33 is not busy. Stated differently, it is unnecessary forthe camera DSP 21 c to perform the processing in real-time, so that dataconversion processing can be executed with priority given to the highpicture quality rather than to the high processing speed and theresulting converted image data may be routed to the memory controller 22via the image data bus 33. The memory controller 22 causes the imagedata to be written in the image memory 32.

The memory controller 22 causes the image data to be read out from theimage memory 32 to route the read-out image data to the JPEGencoder/decoder 29. The JPEG encoder/decoder 29 compresses the imagedata in accordance with the JPEG system to write the compressed imagedata in the recording device 51 shown in FIG. 3.

If real-time processing is not unnecessary, as during recording, the CPU41 permits the pre-set processing to be executed after writing the imagedata transiently in the image memory 32 to exploit the transfer band ofthe image data bus 33 to process the high-pixel image.

The CPU 41 records the image data of the XGA format directly in therecording device 51 in the recording mode. It is however possible forthe resolution conversion circuit 28 to convert the resolution of theimage data before recording the image data on the recording device 51.Specifically, it is possible to cause the resolution conversion circuit28 to convert the resolution of the image data read out from the imagememory 32 via the memory controller 22 in meeting with the VGA(1024×768→640×480) to permit the JPEG encoder/decoder 29 to compress theimage data to record the compressed data in the recording device 51.

If desirous to confirm the as-shot image after image shooting, theoperator thrusts the playback button, not shown, for reproducing theas-shot image.

If the reproducing button is thrust, the digital still camera 1 moves tothe reproducing mode. In the reproducing mode, the CPU 41 controls therespective circuits in the following manner to read out the image dataof the object.

That is, on detecting the thrusting the reproducing button, the CPU 41reads out the image data from the recording device 51 and transientlystores the read-out image data in the DRAM 42 before routing the datavia CPU bus 34 to the JPEG encoder/decoder 29. The JPEG encoder/decoder29 expands the image data read out from the recording device 51 inaccordance with the JPEG system to produce image data of the XGA formatto route the resulting image data via the image data bus 33 to thememory controller 22.

The memory controller 22 writes the image data on the image memory 32and reds out the image data from the image memory 32 to send theread-out image data via the image data bus 33 to the resolutionconversion circuit 28.

The resolution conversion circuit 28 effects resolution conversion sothat the image data will be in meeting with the VGA format(1024×768→640×480 in the NTSC system and 1024×768→640×576 in the PALsystem) to route the converted image data over the image data bus 33 tothe memory controller 22. The image data then is read from the imagememory 32 and routed via the NTSC/PAL encoder 23 to the finder 36. Thisdisplays an image corresponding to the image data recorded in therecording device 51 on the finder 36.

That is, since the image data recorded in the recording device 51 hashigh resolution, the CPU 41 first lowers the resolution and subsequentlyroutes the image data to the finder 36.

It is also possible for the CPU 41 to set, for each of the finder mode,recording mode and the reproducing mode, the order of priority of thecircuits to be processed in preference and to cause the pertinentcircuit to execute the processing in accordance with the order ofpriority on movement to one of the modes. This enables the signalprocessing of image data to be executed efficiently depending on theprocessing contents in each mode.

In the above-described embodiment, it is assumed that the data beingprocessed is the image data equivalent to XGA. It is to be noted thatthe present invention is not limited to this embodiment and can beapplied to, for example, the processing of image data comprised of onemillion or more pixels.

What is claimed is:
 1. An imaging apparatus comprising: imaging meansfor generating image data corresponding to the imaging light from anobject; first resolution converting means for lowering the resolution ofthe image data from said imaging means by way of resolution conversion;second resolution conversion means for raising the resolution of theimage data supplied from said first resolution conversion means over animage data bus by way of resolution conversion; and outputting means foroutputting the image data from said second resolution conversion meanson display means.
 2. The imaging apparatus according to claim 1 furthercomprising: display means for displaying an image corresponding to theimage data from said outputting means.
 3. The imaging apparatusaccording to claim 1 wherein said first resolution converting meanseffects resolution conversion for decreasing the proportion ofoccupation of the image data on said image data bus.
 4. The imagingapparatus according to claim 1 wherein said second resolution conversionmeans effects resolution conversion in meeting with the display standardon said display means.
 5. An imaging apparatus comprising: imaging meansfor generating image data corresponding to the imaging light from anobject; first resolution converting means for lowering the resolution ofthe image data from said imaging means by way of resolution conversion;second resolution conversion means for raising the resolution of theimage data supplied from said first resolution conversion means over animage data bus by way of resolution conversion; storage means forstoring the image data; third resolution conversion means for convertingthe resolution of the image data supplied from said storage means; andoutputting means for outputting the image data from said second or thirdresolution conversion means to display means.
 6. The imaging apparatusaccording to claim 5 further comprising: display means for displaying animage corresponding to the image data from said outputting means.
 7. Theimaging apparatus according to claim 5 wherein said first resolutionconverting means effects resolution conversion for decreasing theproportion of occupation of the image data on said image data bus. 8.The imaging apparatus according to claim 5 wherein said second and thirdresolution conversion means effect resolution conversion in meeting withthe display standard on said display means.
 9. The imaging apparatusaccording to claim 5 wherein the speed of resolution conversion by saidfirst and second resolution conversion means is relatively faster thanthat of said third resolution conversion means.
 10. The imagingapparatus according to claim 5 wherein the imaging apparatus has aplurality of operating modes, and wherein said first and secondresolution conversion means or the third resolution conversion means isselectively used depending on said operating modes.
 11. Arecording/reproducing apparatus comprising: imaging means for generatingimage data corresponding to the imaging light from an object;recording/reproducing means for recording the image data on a recordingmedium and for reproducing the image data recorded on the recordingmedium; first resolution conversion means for effecting resolutionconversion of lowering the resolution of the image data from saidimaging means; second resolution conversion means for effectingresolution conversion of raising the resolution of the image datasupplied from said first resolution conversion means over an image databus; storage means for storing the image data; third resolutionconversion means for performing resolution conversion of the image datasupplied from said storage means; and display means for displaying animage corresponding to the image data from said second or thirdresolution conversion means.
 12. The recording/reproducing apparatusaccording to claim 11 wherein said first resolution conversion meanseffects resolution conversion for lowering the proportion of occupationof the image data on said image data bus.
 13. The imaging apparatusaccording to claim 11 wherein said second and third resolutionconversion means effect resolution conversion in meeting with thedisplay standard on said display means.
 14. The imaging apparatusaccording to claim 11 wherein the speed of resolution conversion by saidfirst and second resolution conversion means is relatively faster thanthat of said third resolution conversion means.
 15. The imagingapparatus according to claim 11 wherein the imaging apparatus has afinder mode of displaying the image data on said display means, arecording mode of recording the image data on said recording medium anda reproducing mode of reproducing the image data from said recordingmedium; wherein if the mode is the finder mode, said first and secondresolution conversion means are used; and wherein if the mode is therecording mode or the reproducing mode, said third resolution conversionmeans is used.